In underground mining, chain scraper conveyors, in particular, for the removal of extracted minerals and also the extraction ploughs of coal plough installations are moved by means of chains which are placed along an extraction face in the top and bottom run and driven by means of chain wheels. The chain wheels are mounted on the machine frame of the respective chain drive so as to be rotatable via bearings arranged in bearing shells and can be driven by means of drives which are detachably coupled to the chain wheels. On account of the normally high power capacities of a chain scraper conveyor or an extraction plough, machine frames with drivable chain wheels are usually used at both ends of the extraction installation. Nevertheless, in the case of relatively short faces, it is also possible for only one of the chain wheels to be driven via its chain wheel shaft. In chain scraper conveyors, each chain wheel shaft usually has two chain starwheels to drive a double chain such as for example a double centre chain. In extraction ploughs, on the other hand, the chain wheel shaft has just one chain starwheel. The chain starwheels have pockets for receiving the usually horizontal links of the link chain in order to deflect the chain and at the same time to drive it in the respectively desired direction.
A chain wheel arrangement of the type in question is known from DE 20 2004 013 198 U1. In this chain wheel arrangement, the bearing shells, which receive the bearings for displacing the chain wheel shaft, form at the same time also those mounting means used to position the chain wheel shaft on the machine frame and axially secure it thereto. The axial distance of the two bearing shells from each other is therefore fixed and one of the bearings is, as the person skilled in the art is generally aware, arranged in a movable bearing system, while the other bearing is designed as a fixed bearing system. In the chain wheel shaft of the type in question, a labyrinth seal arrangement is already used to protect the pair of sliding ring seals between the chain wheel and bearing as effectively as possible from contamination with fine coal and water. The labyrinth seal arrangement is achieved by an annular web-shaped projection on a connection piece and also by a groove in the lateral flank of the chain wheel which engage with each other with play, thus allowing the chain wheel shaft and connection piece to rotate relative to each other.
Within the known chain wheel arrangement, in particular the labyrinth seal arrangement used there, allows a relatively long service life of the chain wheel arrangement and also of the bearings used to be achieved without maintenance work. The assembly of the chain wheel arrangement of the type in question is nevertheless relatively complex, as spacer bushes and clamping sleeves have to be fitted in order to hold the bearing rings of the respective bearings in position. Furthermore, increased soiling of the sliding ring seals is displayed after a large number of operating hours on account of an increase in the play within the labyrinth seal arrangement.
DE 29 42 916 C2 discloses a machine frame for a chain conveyor, the side cheeks of which comprise openings for receiving the bearing shells. The bearing shells are welded onto the side cheeks, which are thickened to this end.